power_supply: add CHARGE_COUNTER property and olpc_battery support for it

This adds PROP_CHARGE_COUNTER to the power supply class (documenting it
as well).  The OLPC battery driver uses this for spitting out its ACR
values (in uAh).  We have some rounding errors (the data sheet claims
416.7, the math actually works out to 416.666667, so we're forced to
choose between overflows or precision loss.  I chose precision loss,
and stuck w/ data sheet values), but I don't think anyone will care
that much.

Signed-off-by: Andres Salomon <dilinger@debian.org>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>

drivers/power/olpc_battery.c

@@ -19,7 +19,7 @@
 
 #define EC_BAT_VOLTAGE	0x10	/* uint16_t,	*9.76/32,    mV   */
 #define EC_BAT_CURRENT	0x11	/* int16_t,	*15.625/120, mA   */
-#define EC_BAT_ACR	0x12
+#define EC_BAT_ACR	0x12	/* int16_t,	*416.7,      µAh  */
 #define EC_BAT_TEMP	0x13	/* uint16_t,	*100/256,   °C  */
 #define EC_AMB_TEMP	0x14	/* uint16_t,	*100/256,   °C  */
 #define EC_BAT_STATUS	0x15	/* uint8_t,	bitmask */
@@ -289,6 +289,14 @@ static int olpc_bat_get_property(struct power_supply *psy,
 		ec_word = be16_to_cpu(ec_word);
 		val->intval = ec_word * 100 / 256;
 		break;
+	case POWER_SUPPLY_PROP_CHARGE_COUNTER:
+		ret = olpc_ec_cmd(EC_BAT_ACR, NULL, 0, (void *)&ec_word, 2);
+		if (ret)
+			return ret;
+
+		ec_word = be16_to_cpu(ec_word);
+		val->intval = ec_word * 4167 / 10;
+		break;
 	case POWER_SUPPLY_PROP_SERIAL_NUMBER:
 		ret = olpc_ec_cmd(EC_BAT_SERIAL, NULL, 0, (void *)&ser_buf, 8);
 		if (ret)
@@ -317,6 +325,7 @@ static enum power_supply_property olpc_bat_props[] = {
 	POWER_SUPPLY_PROP_TEMP_AMBIENT,
 	POWER_SUPPLY_PROP_MANUFACTURER,
 	POWER_SUPPLY_PROP_SERIAL_NUMBER,
+	POWER_SUPPLY_PROP_CHARGE_COUNTER,
 };
 
 /* EEPROM reading goes completely around the power_supply API, sadly */